How seat and torque new A/T plug adapter 722.623 ???

How seat and torque new A/T plug adapter 722.623 ???

Question #1:
I installed a new A/T plug adapter.
Need know how the large O-ring seats.
Should the O-ring be visible, nesting between the adapter and trans housing ...
or should the O-ring be NOT be visible--completely within the trans housing?

Question #2:
I tightened the bolt in center of adapter tight w/o a torque wrench, then backed it out a bit and tightened again, gently. Could not find any torque setting for this small bolt. Does anyone know this torque setting ?

Thanks

PS. Am obviously doing the trans change/flush thing, and have stopped until I get some additional info, so that I don't cruise down the road leaving a fluid trail.